Transmission mechanism having deceleration function

Abstract

A transmission mechanism having a deceleration function includes a guide screw, a worm wheel set, an intermediary ring, an isolator and a passive sleeve. The worm wheel set is fitted onto the guide screw and includes worm wheel and plural claw arms. A spacing slot is formed between any two adjacent claw arms. The intermediary ring is fitted onto a peripheral edge of each claw arm. The isolator surrounds a peripheral edge of the intermediary ring with one side fixed to an actuator. With plural grooves arranged on a peripheral edge thereof, the passive sleeve is fitted onto the guide screw. An accommodation space is formed among the groove, spacing slot and intermediary ring. Each needle roller is accommodated in the accommodation space and inter-contacted with the claw arm, the intermediary ring and the passive sleeve.

1. A transmission mechanism, having a deceleration function, used in a linear actuator having a worm, including:
 a guide screw; 
 a worm wheel set which is fitted onto one side of the guide screw and includes a worm wheel driven by the worm to rotate and a plurality of claw arms extended outwardly from one side of the worm wheel; a spacing slot being formed between any two adjacent claw arms; 
 an intermediary ring which is fitted onto peripheral edges of the claw arms and rotatable with respect to the worm wheel set; 
 an isolator which surrounds a peripheral edge of the intermediary ring with one side fixed to the actuator for limiting the intermediary ring to rotate in a single direction as clockwise or counterclockwise and stops the intermediary ring in an alternative direction; 
 a passive sleeve, with a plurality of grooves arranged on a peripheral edge thereof, fitted onto the guide screw by being linked to each other, an accommodation space being formed among each groove, the spacing slot, and the intermediary ring; and 
 a plurality of needle rollers, each of which is accommodated in the accommodation space and is always inter-contacted with the claw arm, the intermediary ring, and the passive sleeve; 
 wherein, when the worm wheel is driven to rotate, the claw arms push the needle rollers and the intermediary ring to rotate and, since the intermediary ring is wedged and stopped by the isolator, the frictional force to hinder the rotation driven by the claw arms to the needle rollers and the intermediary arms is increased, lowering down rotational speeds of the passive sleeve and the guide screw. 
 
     
     
       2. The transmission mechanism having deceleration function according to  claim 1 , wherein the worm wheel set is made of a plastic material. 
     
     
       3. The transmission mechanism having deceleration function according to  claim 1 , wherein the isolator is a coil spring, and a rotational direction of which is the same as that of the worm wheel. 
     
     
       4. The transmission mechanism having deceleration function according to  claim 1 , wherein the isolator is a coil spring, and a rotational direction of which is the same as that of the guide screw. 
     
     
       5. The transmission mechanism having deceleration function according to  claim 1 , wherein the plurality of grooves of the passive sleeve is configured as a “V”shape. 
     
     
       6. The transmission mechanism having deceleration function according to  claim 1 , further including a limit block cover fitted onto one side of the passive sleeve and extended outwardly by covering the needle rollers for restricting movement of the needle rollers. 
     
     
       7. The transmission mechanism having deceleration function according to  claim 1 , wherein the actuator includes a lower seat body which comprises an embedded slot into which a positioning section that extends outwardly from a coil spring is inserted.